Projectile



NOV. 4, 1952 R 0, FRAN-TIK 2,616,372

PROJECTILE Filed Aug. 2, 1945 Ffm INVENTOR UPN FW'K ATTORNEY Patented Nov. 4, 1,952

PROJECTILE Rudolph 0. Frantik, Albuquerque, N. Mex., assignor to the United States of America as represented by the Secretary of the Navy Application August 2, 1945, Serial No. 608,599

3 Claims.

This invention relates to rotary projectiles of the type which includes a sub-caliber core having a substantially full-caliber sabot for supporting and centering the core in a gun .barrel the sabot being releasable from the core when the projectile emerges from the gun muzzle. More particularly, the invention pertains to a sabottype projectile in which the discardable portions are released by a delayed centrifugal action, thus permitting the projectile to be red safely through a muzzle brake.

It is, therefore, an object of the invention tc provide an improved sub-caliber projectile having sabot and bourrelet portions of novel design adapted to be shed from the core by centrifugal action.

It is another object of the invention to provide a sub-caliber projectile capable of retaining its discardable parts until the entire projectile assembly has emerged from a muzzle brake attached to the ring gun,

It is a further object of the invention to provide a sabot for sub-caliber projectiles having forwardly and rearwardly extending segmented cup portions integral with a continuous annular structure and supported thereby in cantilever fashion, such that a moment in the cantilever cup portions on one side of the annular structure will add algebraically to any moment in the cantilever cup portions situated on the opposite side of the annular structure. Thus the centrifugal force acting to separate the forwardly extending cup portions from the core will be substantially counter-acted by the sum of the centrifugal force acting upon the rearwardly extending cup portions and the outward radial thrust of the high pressure gases acting upon such rearward cup portions until the projectile assembly has emerged from the high pressure area (e. g. a muzzle brake), when the pressure exerted on the rear end of the sabot falls off and can no longer contribute to the moment acting on the rear cup portion.

It is an additional object of the invention to provide a sub-caliber projectile which is simple in construction, has relatively few parts, and may be easily assembled.

These and other objects and advantages of the invention may be better understood by reference to the accompanying specification and drawings in which:

Fig. 1 is a side elevational view, partlyin section, of a sub-caliber projectile made in accordance with the invention;

Fig. 2 is a longitudinal sectional view of the sabot;

Fig. 3 is a. longitudinalsectional view of the bourrelet employed with my projectile;

Fig. 4 is a side elevational view of the subcaliber core.

` Referring to the drawings, the projectile assembly shown in Fig. 1 comprises a core II having a modified ogive I2. A substantially fullcaliber bourrelet I3, weakened along its length by cuts I4 but with an integral uncut annular ring I6, is positioned snugly on the core and is restrained from longitudinal movement thereon by the engagement of a shoulder I1 on the bourrelet with a shallow annular groove I9 in the core. A bearing ring 20 of steel or the like is rigidly secured, as by threads (undesignated), forward on the bourrelet and, by contacting the lands of the bore, serves to maintain the projectile assembly in proper alignment in the gun barrel.

A sabot designated generally at 2|, also weakened along most of its length as by cuts 22, is firmly secured by means of thread course 23 on the rearward end of the core Il. A relatively narrow continuous ring 2B, preserved in the sabot between the adjacent ends of the cuts 22, supports in cantilever fashion the rearward segments 25 and the forward segments 26 of the sabot formed by the weakening cuts. A frangible turning band 21, of copper or the like, is press-fitted onto the sabot and is restrained against relative longitudinal movement with respect thereto through the agency of a plurality of annular grooves 28 cut into the exterior surface of the sabot. The rear segments 25 form a cupped rear end upon the assembled projectile, as shown, and are provided with a sloped inner peripheral surface 3l adapted to confine the gases formed in the combustion of the propellent charge, resulting in an outward radial thrust on the segments. f

When a projectile made in accordance with my invention, for example the projectile illustrated in Fig. 1, is fired from a gun the centrifugal force resulting from the high rotational velocity of the projectile produces moments in the forward segments 26 and rear segments 25 of the sabot tending to move them outward from the core using the annular ring 24 as the pivot. Since the moment in each forward segment 26 is counter to that in the corresponding rear segment 25, these moments tend to counteract one another; however, since the moment arm and mass of the segment 26 are both larger than they are in segment 25 the moment in the latter resulting solely from centrifugal force would be insumcient to balance the moment in segment 26 and so to prevent separation of that segment from the core. An additional moment is produced in the rear segments 25, however, by the gas pressures within the muzzle brake. The muzzle brake, by preventing free expansion of the gases until the projectile has left it, momentarily and partially retains the pressure, and a tremendous outward radial thrust is thereby irnposed upon the sloped surfaces 3| of the rear segments. By properly designing the cup formed by these rear segments, a sufcient radial thrust due to gas pressure may be obtained to augment the centrifugal force acting on the rear segments 25 so that the sum of the moments thus produced will at least equal the moments in the forward segments 26, thus preventing the separation of the sabot from the sub-caliber core until after the projectile assembly has emerged from the muzzle brake. After leaving the muzzle brake the gas pressures acting upon the rear segments 25 fall oi rapidly, thereby eliminating the moments due to gas pressures acting upon the rear segments 25. vThis results in an unbalanced system of moments acting upon the sabot assembly with the moments acting upon the forward segments 26 now greatly exceeding those acting upon the rear segments 25. Forward segments 26 then move outwardly under centrifugal force from the core Il and, since they are integrally supported by the annular ring 24, they tend to fold backward upon the sabot assembly. Wind resistance acting upon the greater area of segment 25 thus exposed accelerates this opening action. Wind resistance, thus combined with centrifugal force, assists in bending segment 26 rearwardly with such force that annular ring 24 is torn completely through its thickness and the entire sabot assembly is thereafter immediately shed from the core by centrifugal force,v The bourrelet I3, no longer confined by the sabot, is shed from the core Il by a combination of centrifugal force and cantilever action which ruptures the uncut portion I6 of the bourrelet as well as the bearing ring 20.

While what has been described -is particularly illustrative of a presently preferred embodiment of my invention, it is not intended that the scope of the invention be` limited thereto but'that it embrace any modifications and changes which fall within the true spirit of the invention, as covered by the appended claims, occurring to those skilled in the art.

I claim:

1. In a projectile of the rotary type adapted to be fired from a gun, a sub-caliber core, a sub- 4 ing the rifling of said gun, a. ybourrelet fitted snugly on said core, and a substantially fullcaliber bearing ring fixed to said bourrelet for engaging the lands of the bore of said gun, said sabot having a rear cup portion and a forward cup portion integral with said sabot, said forward cup portion adapted to hold said bourrelet on said core, said bourrelet having a .plurality of radial weakening cuts to facilitate its disintegration under centrifugal force, said sabot having a plurality of radial weakening cuts from the rear end thereof substanti-ally to the base of said rear cup portion and a corresponding number of radial weakening cuts from the forward end thereof at least to the base of said forward cup portion, the segments thus formed being supported by cantilever action from the uncut porstantially full-caliber sabot threaded on said,

core, a turning band fixed to said sabot for engagtion of said sabot.

2. Construction as described in claim 1 in which the area of the yinner peripheral surf-ace of said rear cup portion is such that the moment produced therein by the gas pressure resulting from combustion of the propellent charge substantially equals the moment produced in the segments of said forward cup portion by centrifugal force, thereby maintaining said forward cup portion adjacent said bourrelet, until the pressures acting on said sabot have decreased' below a predetermined value.

3. Construction as described in claim 1 in which the area of the inner peripheral surface of said rear cup portion is such that the sum of the moments produced therein by the gas pressure resulting from combustion of the propellent charge and by centrifugal force at least equals the moments produced in the segments of said forward cup portion by centrifugal force, thereby maintaining said forward cup portion adjacent said bourrelet, until the gas pressures acting upon said sabot have decreased below a predetermined value.

RUDOLPH O. FRANTIK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,973,604 Brandt Sept. 11, 1934 FOREIGN PATENTS Number Country Date 13,575 Great Britain Oct. 14, 1884 131,034 Great Britain Aug. 21, 1919 496,991 France Aug. 25, 1919 

